Effect of pre-deformation homogenization on high-temperature deformation behavior and microstructure evolution of a new Ni-W-Cr superalloy

Abstract

To address the challenges posed by high tungsten (W) content (≥26 wt.%) in a novel Ni-W-Cr alloy designed for next-generation molten salt energy systems, which leads to segregation of refractory elements and difficulties in conventional thermal deformation processing, the effects of pre-deformation homogenization on deformation behavior and microstructural evolution have been investigated. Techniques including scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) were employed for analysis. A novel homogenization heat treatment method was developed for Ni-W-Cr alloys with elevated refractory element content. Pre-deformation introduces a range of defects, including dislocations and substructures, which act as diffusion channels, facilitating the rapid transport of elements and promoting the dissolution of refractory segregation phases, thereby significantly reducing homogenization time. Moreover, pre-deformation homogenization enhances the reprecipitation of carbides by dissolving large primary carbides into finely dispersed particles, strengthening grain boundaries and minimizing crack initiation at weak boundary regions. Additionally, dislocations and other defects serve as nucleation sites for dynamic recrystallization (DRX), promoting an additional continuous dynamic recrystallization (CDRX)-assisted nucleation mechanism. This mechanism significantly enhances DRX nucleation, thereby improving the hot workability of the alloy.